Creating a Disk Image sounds a bit frightening but it is soooooo simple. All you need is Macrium Relect Free. Fire it up and click on the Wizard. A Disk Image is an exact copy of all the Programs, Data and Operating System and this enables you to restore that image to a new hard drive or in case of malware infection, it will let you overwrite everything. By doing regular virus checks and system de-cluttering and making Disk Images, you are prepared for the worst.
I recommend using an external USB Hard drive to store the backup/ Image. You can use a USB flash drive/ Stick but in my experience, External Hard drives are more robust and reliable.
For the DESTINATION, below, select Folder and then choose your External Hard drive or if you have a home LAN, you could choose a network share.